1. Field of the Invention
The present invention is related to a conductive wire pattern of a pad area and a method of monitoring a bonding error of a film, and more particularly, to a conductive wire pattern of a pad area that can serve as a reference basis of monitoring a bonding error of a film and the method of monitoring the bonding error thereof.
2. Description of the Prior Art
An array substrate and a color filter (CF) substrate are separately fabricated in the general fabrication of a liquid crystal display (LCD). The fabrication of the array substrate includes several steps of semiconductor process such as thin film deposition, photolithography, and etching processes in order to fabricate thin film transistor (TFT) array. The CF substrate includes color filters corresponding to the TFTs or pixels in an array arrangement on a substrate. After the fabrication of the array substrate and the CF substrate are completed, attachment of the two substrates would been taken place followed by a breaking or segmenting process.
Please refer to FIG. 1. FIG. 1 is a schematic diagram of a conventional LCD panel 10. The conventional LCD panel 10 includes a CF substrate 12 and an array substrate 14, wherein the CF substrate 12 is smaller in size than the array substrate 14. Thus, part of the array substrate 14 would be exposed by the CF substrate 12. The exposed array substrate 14 by the CF substrate 12 is usually determined as the non-display region 16. A plurality of terminals are disposed within the non-display region 16, so as to electrically connect the wires of the internal wires of the LCD panel 10 such as scan lines or signal lines to an external control circuit. Please refer to FIG. 2. FIG. 2 is a schematic diagram of a part of a terminal 20 of the LCD panel 10 of FIG. 1. In general, the terminal 20 includes an opening portion 22 and a line portion 24, wherein the main function of the opening portion 22 is to transfer external control signals to the internal wires of the LCD panel 10. Thus, when the fabrication of the LCD panel 10 is completed, films such as printing wire board (PWB) films are usually bonded to the non-display region 16, and the conductive wire pattern on the films is electrically connected to the opening portion 22 for transferring the external signals. As shown in FIG. 3, when the film (not shown) is bonded to the non-display region 16, the conductive pattern 26 on the surface of the film is supposed to cover the center portion of the terminal 20, thus enabling the distances d1 and d2 between the conductive pattern 26 and the both sides of the opening portion 22 to be equal.
However, in the process of bonding/attaching the film, there are possibilities that mismatch on the machine or tool lead to errors of the bonding location. As shown in FIG. 4, since a bonding error (or so called attaching aberration) of a film occurred, the conductive pattern 26 on the film is displaced to near the right side of the terminal 20, such that the distance d1, the distance between the conductive pattern 26 and the left side of the opening portion 22, is larger than the distance d2, the distance between the conductive pattern 26 and the right side of the opening portion 22. From the above, it is concluded that there are inevitable bonding error in the conventional film bonding technology; it is therefore the bonding error of attaching a film must be monitored. The conventional method of testing the bonding error of a film can be classified into three types, one of which is utilizing sensors including charge coupled device (CCD) for carrying out the test. The detector must utilize a CCD sensor to search for the non-display region 16 and make sure if bonding error of a film occurred. If a bonding error is determined, the shifted length of the film is then calculated by the scale ruler of the CCD sensor. However, the shortcomings of this kind of test include that the LCD panel 10 has to be especially delivered to the machine with the sensor so as to carry out the test. Besides, the detector has to use the CCD sensor to search for the location of the targets of the test with consuming much time and there are possibilities that no errors be detected. In addition, there are requirements of the standards of the sensor, for instance, the sensor needs to scales of measurement and the built-in measuring programs. Furthermore, the accuracy of the test is questionable.
In the second type of conventional method of testing the bonding error of a film, a detector will directly use measuring tools to detect the bonding error between the terminals 20 and the conductive pattern 26 after bonding the film. Bonding error of a film and the shifted distance to the left or to the right may be determined through measuring the distance d1 and the distance d2, where the distance d1 represents the distance between the conductive pattern 26 and the left side of the opening portion 22, and the distance d2 is the distance between the conductive pattern 26 and the right side of the opening portion 22. However, the shortcomings of this measure method include troublesome testing procedures and lack of accuracy.
In another aspect, the third conventional method of testing the bonding error of a film is utilizing the shifting measuring mark to measure the distance of the error of the film. First, a shifting measuring mark 30 is formed by exposure on the array substrate 14. As shown in FIG. 5, the shifting measuring mark 30 includes three sub-marks 30a, 30b, 30c, which are triangles with vertex angle facing the top. A shifting measuring mark 32 in the form of an up-side-down triangle is formed on the film, too. When the film is bonded to the terminals 20 without error (as the relative position of the terminals 20 and the conductive pattern 26 on the left of FIG. 5), the vertex angle of the up-side-down triangle in the bottom of the shifting measuring mark 32 on the film will meet the mid-point of the shifting measuring mark 30, the vertex angle of the sub-mark 30b in the middle of the shifting measuring mark 30. Please refer to FIG. 6. FIG. 6 illustrates the condition when bonding error of a film occurs. As shown on the left of FIG. 6, the bonded film shifted to the right for a certain length, the vertex angle of the shifting measuring mark 32 happens to meet the vertex angle of the sub-mark 30c of the shifting measuring mark 30. It is therefore determined that the film is shifted to the right for 3 micrometers (um). However, there are still shortcomings of the third measure method: due to the imaging limitation of the exposure machine, patterns smaller than 3 um may not be formed. The sharp points of the vertexes of the triangle patterns may not be perfectly formed as well, and a rounded pattern may be obtained. Thus accuracy of the measurement of the shifted length would be influenced.
Therefore, the method on how to determine if a bonding error of a film occurred and how to measure the bonding error of a film in an easy and efficient way remains as important issues in the LCD panel industry.